leaking between tub faucet and wall when shower is on - HELP pls!

I just replaced my tub faucet since the previous diverter gate was cracked and would leak when the shower was on. It's not leaking from the faucet anymore but when i close the diverter gate to start the shower water leaks out from the back end of the faucet, btwn the faucet and the wall. It does not leak out of there when the diverter gate is open however. If I just run the water out of the faucet and do not close the gate to start the shower it seems fine. I wrapped treads with teflon tape before attaching the tub faucet but I have not caulked around the faucet. Do you think a little caulk would fix the problem or is it something bigger?

Don't caulk around the faucet, Christine. That would just make the water go behind the wall. You definitely don't want that! I would remove the faucet and start over. Clean off all the old tape that you put on. Then re-tape, using a few more turns than you used the last time. Remember to always tape in such a way that turning the faucet does not unravel the tape. I think that would be in a clock-wise direction in your case. You might also purchase some pipe dope and apply it after taping as extra insurance towards good seal. Of course, if you bought a plastic faucet and cracked the threads (or stripped them) this does not apply. Also, if you loosened the fittings behind the wall when tightening the faucet. (Not a plumber, just a lowly handyman.)

Thanks Bob. I will try it again but... what if i did strip or crack the threads ? how will i know? it is plastic and i may have twisted it too far the first time but it still seems to twist on ok. I just hope I didn't break it. I will try again. Thanks for the advice.

If the threads are cracked, no matter what you do you wont be able to get it to stop leaking. When you remove the faucet to try it again, inspect the threads on the faucet body closely to see if there are any signs of cracks and/or evidence of the faucet being cross threaded when first installed.